The present invention relates to a device of novel design for use in the installation of horizontally-disposed siding to the exterior surface of structures, two or more of the devices functioning to support and precisely position a length of siding during installation. Without the aid of such tools, the procedure for the installation of horizontally-disposed siding requires much careful measuring, leveling, marking and monitoring to assure that the individual lengths of siding are properly and uniformly positioned relative to the rest. Not only is said procedure time and labor inefficient, but it also provides abundant opportunities for human error. What the present invention provides is a quick, easy and virtually foolproof approach to the installation of horizontally-disposed siding.